dummy_queue/
lib.rs

1pub struct Queue<T> {
2    head: Option<Box<Node<T>>>,
3    tail: Option<*mut Node<T>>,
4}
5
6pub trait TQueue<T> {
7    fn new() -> Self;
8    fn enqueue(&mut self, item: T);
9    fn dequeue(&mut self) -> Option<T>;
10    fn len(&self) -> usize;
11    fn front(&self) -> Option<&T>;
12    fn is_empty(&self) -> bool;
13}
14
15struct Node<T> {
16    value: T,
17    next: Option<Box<Node<T>>>,
18}
19
20impl<T> Queue<T> {
21    pub fn new() -> Self {
22        return Queue {
23            tail: None,
24            head: None,
25        };
26    }
27
28    pub fn enqueue(&mut self, item: T) {
29        let new_node = Box::new(Node {
30            value: item,
31            next: None,
32        });
33
34        let raw_node = Box::into_raw(new_node);
35
36        if let Some(tail) = self.tail {
37            unsafe {
38                (*tail).next = Some(Box::from_raw(raw_node));
39            }
40        } else {
41            self.head = unsafe { Some(Box::from_raw(raw_node)) }
42        }
43
44        self.tail = Some(raw_node);
45    }
46
47    pub fn dequeue(&mut self) -> Option<T> {
48        return self.head.take().map(|head| {
49            self.head = head.next;
50
51            if self.head.is_none() {
52                self.tail = None;
53            }
54
55            head.value
56        });
57    }
58
59    pub fn len(&self) -> usize {
60        let mut counter = 0;
61        let mut current_node = &self.head;
62
63        while let Some(node) = current_node {
64            counter += 1;
65            current_node = &node.next;
66        }
67
68        return counter;
69    }
70
71    pub fn front(&self) -> Option<&T> {
72        return self.head.as_ref().map(|node| &node.value);
73    }
74
75    pub fn is_empty(&self) -> bool {
76        return self.head.is_none();
77    }
78}
dummy_queue/lib.rs

dummy_queue/
lib.rs
